Unresponsive HP-42s


I've "taken in" 4 42s in need of aide.

They are all disassembled at this point. Two were delivered to me apart. One of these is hopeless with a destroyed processor. The second one is very dirty.

The last two have hope, I think, but need the forums help.

Unit 3 was taken apart and cleaned. I re-assembled and got it to turn on after batteries are installed. However it seems to be bogged down with something and will either be very slow to respond to keystrokes or not at all.

Unit 4 starts up after putting batteries in, but will not respond to any keystrokes.

They both seem to have similar ailments. Is it dirty/bad keyboards?


Have you checked the foam insert residing under the keyboard pca to logic pca flex pcb.

These have a tendency to compress over time resulting in a lost connection causing unresponsive keys or whole keyboard.

Assemble one and then press gently on the frame between the lower LCD panel and the top of the keys. While pressing at that location also test the keyboards unresponsive keys. If they work it is definitely the foam which must be replaced.

I use an older foam mouse pad as a donor.



I've tried that. Cleaned the contact with alcohol and "erased" the gold contact. No matter how hard I push, it does not change.

I think I need to go through the keyboards and test using Randy's Diagram

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